According to Aldrimer, authorities in the Scandinavian country notified NATO of a serious, ongoing cyber attack by a hacker group linked to Russian intelligence. That was not the official story. The Swedish Civil Aviation Administration told the world that a solar storm had knocked out air traffic control systems in much of Sweden.
Sweden is not a member of NATO, but it issued the warning to the alliance and several NATO allies, including Norway and Denmark. The Swedes believed the cyber attack was led by the Advanced Persistent Threat (APT) group which previously has been linked to the Russian military intelligence service GRU.
Of course no one is commenting officially. But it does not appear to have been the only attack on the Swedes. Another case also sent NATO included an attack on the state-owned power company Vattenfall. Vattenfall owns and operates several nuclear power plants in Sweden and Germany.
The Swedish Civil Aviation Administration’s computer problems were pretty serious. They made it impossible for air traffic controllers to see the aircraft on their screens. Air traffic to and from the Arlanda, Landvetter and Bromma airports in Sweden was affected, and many domestic and international flights were cancelled.
To be fair to the Russians there were warnings of an impending solar storm in the period around the air traffic control collapse. But it was expected to be moderate and declining.